So `\text{Hi}` becomes one <span...>Hi</span>, rather than two
<span...>H</span><span...>i</span>.
This allows the font renderer to apply kerning, which changes some
test output.
Summary:
This diff provides support for Latin-1, Cyrillic, and CJK characters
inside \text{} groups. For Latin-1 and Cyrillic characters we use
glyph metrics from a glyph from Basic Latin that has roughly the same
bounding box. We use the metrics for a capital 'M' to approximate the
full-width CJK characters. Half-width characters are not supported yet.
Test Plan:
- make test
- make screenshots
Reviewers: emily